The main goal of this study is to identify potassium channel genes and are expressed in mudpuppy taste receptor cells and encode channels localized to the apical membrane. Apically restricted, voltage-dependent K+ channels reportedly are involved in the transduction of bitter and sour taste in the mudpuppy. At this time, the molecular details of these channels are unknow The apical K+ conductance of mudpuppy taste cells consists of several different voltage-dependent K+ currents. Based on pharmacological profiles and gating properties, it is likely that genes encoding this population of K+ channels include members of two known K+ channel gene families: Kv2 and Slo. Channels encoded by members of both of families produce currents which are very similar to those expressed in mudpuppy taste cells. Thus, to identify taste cell K+ channel genes, a mudpuppy taste cDNA library will be screened at reduced stringency with probes for Slo and Kv2. Cloned K+ channel genes will be sequenced and characterized and their expression pattern will be investigated using in situ hybridization and single cell reverse transcriptase polymerase chain reaction. For physiological analysis, the cloned genes will be expressed in Xenopus oocytes. The characterization of taste cell K+ channel genes proposed in these studies will enable further investigations into the molecular nature of the interactions between taste cell K+ channels and tastants, channel blockers and intracellular proteins. In addition, manipulation of the cloned channel gene sequence may reveal the mechanisms responsible for the unique apical localization of the channels in taste cells.